slickescort1981

For a while my 1.8 zetec (105ps) has had a prob. Every now and then when i go to pull away itll misfire or when say sittin on motorway holdin the revs itll do the same and lose power. its confusing me as when u full throttle it clears and runs fine till u go back to part throttle. i serviced it which cleared it for a week but now its back. it blew a rad hose the other day so got a new one, new coolant etc and cleaned out the idle control valve whilst i was at it. not its terrible and will only really pull away at near full throttle otherwise it misfires. any help gratefully received guys, and girls, of course

xr3iturbo

dodgy tps(throttle position sensor) or earth to tps ,sound like something is spiking causing the ecu to do this


tommy

nick series1

There are certain Spark plugs which have a too small ceramic diameter causing the plug lead to short down the side of the plug to the head.
I think ford used to put some special (non conducting) jelly in the plug leads to stop this.
I had a 105 zetec - used to missfire at random points for the three years i owned it - no logic to it - got pissed off - sold it then spoke to a ford mechanic and that is what he told me !!

You need to buy some specific make plugs - sorry can't remember the make that work. I would think that Motocraft ones would be ok - from ford !!

slickescort1981

thanks lads, changed the tps bout five months ago as it was runnin ok but idling at well over 1500rpm, and thought the tps wasnt sitting back properly after throttle had been used coz everytime i revved it it got higher. might give the plugs a try as it seems like its doin that. it can be perfect one second then shit the next, thanks again!

johnny99

Doubt that it's caused by the plug's, as when you accelerate, there under more pressure, thus the misfire should get worse, and be ok when cruising. I would try a lambda sensor.

John

Tarren

agree

slickescort1981

thats a good point actually, plus i just remembered i only changed the plugs about 6weeks ago. i was thinkin of checkin for a vacuum leak on the inlet somewhere but as that would produce more vacuum when accelerating, just like the plugs it should get worse in theory. cheers guys

nick series1

I didn't read the symptoms properly -
The lead side of the plug has more pressure when accelerating ?? Not sure what you mean ??

Anyway - from experience these can cause funny problems - all i'm saying is whip off the leads and quickly look at the end of the lead and see if it has been arking - it'll literally only take 30 seconds to do.

I'm assuming when you run it flat out to clear it - you have the clutch down therefore the engine has no load ?? And this porblem really only appears when the engine is under load ??

slickescort1981

its same either way, i can rev it at astandstill and itll rev fine, then pull away at part throttle and it misses and loses all power. so u have to full throttle to pull away. if that makes sense? in other words doesnt matter if drivin or sittin still and itll accelerate perfect on full throttle but nothin less. sorry if im bein a pain in the arse, im normally pretty good wiv cars but this has got me stumped. think im gonna have to change idle control valve anyway as once its warmed up a bit it badly hunts and occasionally stalls now. cheers

nick series1

Then perhaps as Johny99 said the lambda snesor could be the one.

It's relatively easy to check - I think anything under 0.5V gives it the "Lean" signal (ie it's running lean) and over 0.5V the "Rich" signal.

I await to be corrected on this !! But i'm pretty sure that the above are the figures to use. Find the pins on the ecu which are the signal from the Lambda - get your mate with a multimeter in the footwell and go for a short drive - you should see if this is giving the correct signal. There maybe a standard resistance "At rest" if you like which could give you a good idea as to the condition of it.

slickescort1981

cheers for that ill give it a try soon and let u know how it goes.

xr3iturbo

dont think it will be iscv as that only lets more air in in cold conditions also controlled by the ecu, i think you should mesure the risistance across the tps pins and move it slowley and look at the metre and look out for the reading sticking at some point of moving the throttle from closed to fully open

also check the lambda


also had prob once with zetec turbo and the coilpack at the top were the pegs are for the plugs to go on the spark was flying across the coil pack, pop the bonnet and have a look when its dark



tommy

slickescort1981

replaced tps a few months back when problems started. replaced idle control valve yesterday anyway as it wouldnt even tick over anymore. it solved that problem as it was now ticking over but hunting pretty badly. disconnected lambda and engine revved up fine and when it was plugged back in it ran crap again. took it for test drive with no lamda plugged in and it drives ok. so now ordered a new one and should get it tues. so well done to anyone who got that right. ill let u know how goes but thanks everyone for ur help, im fairly new on here so its helped no end